Microwave and millimeter wave wide-band three-dimensional (3-D) synthetic aperture radar (SAR)-based imaging techniques have demonstrated tremendous usefulness for nondestructive evaluation (NDE) applications for industrial, scientific, and medical imaging. For example, such techniques are particularly useful for 3-D imaging of low contrast dielectric media and in security applications. Typically, measurements are performed by raster scanning a probe on a uniform 2-D grid. To achieve optimum resolution and image quality, however, a large quantity of measurements must be obtained to image even a small area. Unfortunately, conventional scanning techniques require a relatively long time to scan and obtain an image. For example, the time needed to perform the measurements typically ranges from tens of minutes to several hours depending on the size of structure being imaged and the operating frequency. As a result, nondestructive testing of large and critical structures (e.g., aircraft, bridges, space vehicles and the like) cannot utilize real-time imaging.
A method to form SAR images as quickly as possible is desired.